Liquid rheostat



July 1952 H. v. CRAWFORD ETAL 2,602,125

LIQUID RHEOSTAT Filed Dec. 31, 1949 zar Inventor's. Henry V-CrawForcl,Leland J. Parkinson,

Their- Attorney.

Patented July 1, 1952 V-. Grawfordand Leland J. rarkinson,

f- Schenectady; N; Y., assignors to-General Elec trio Company; a;corporationiot New York nnl eat nnlleszemhe i 1 nafseramol new.QLClaims. (Cl. sol-57 )1 This, nvention ela s, q iau iif e and for;ts'p' ir i al'obi e-n v i n ir w.

.R an mpl r hepstats; 11 1 11 imthet; obje of h nv o s, to provide aliquid rheostat'in which the-electrodes are stationary and thellevel ofthe electrolyte "is variable.

, Another object oi'the invention is the provision of; atliquidrheostathaving smooth steplessvariation of 'resistaneeover theentire range ofresistance.

A; furtherobject fthe invention is to provide alliquid; rheostatghavingno wearing parts.

A further, object oi-our invention is the provision of improved coolingmeans for a liquid rheostat, to enable apparatus of a given capacitytobe made smaller and simultaneously to minimizeboiling, fuming; and thelike, ofthe elec trolyte.

A stillfurtherobjeot off-the invention is the provision, ;in a liquidrheostat having afloatable electrolyte tank,'of rmeans for, preventingeontamination of theeleotrolyte in. the eventthe level of-the liquid: inWhiohfthe tankisfioating rises abnormally high and exceeds the height ofthe-top of; the tank.

Other objects will be apparent asthe description-of the inventionproceeds.

In carrying out our invention in one form, we-provide; a tank'forcontaining the electrolyte which i s-floated in a liquidhavingaVariable level. -A fixed support isprovided-abovegthe liquid and fromthis support" are suspendedjthe electrodes-in the electrolyte. As thelevel-of; the liquid, rises; increased portions of I the-eleotrodes aresubmerged and the resistance of the liquid rheostat decreases, As theliquid level; falls; the opposite occurs and the rheostat resistanc isincreased;

For a clearer and mor e complete. understanding of "the invention,reference; should be had to, the accompanying drawing in whichyFig. '1is an elevation view; 7 partially ,in section; of; a pref erredembodiment of the invention; whileliigiz is a sectionalvieW-alongtheline 2-2 of Big; 1',

i the ra n our nvention. is llus ra ed embodied in a preferred form as aslip regulator for a t r ha e ouml otqr ind cation motor I he quid rheosat li e ula or. isidesi nated generally by the numeral; l0,""ijherheo'stat. It m se a l a ah e ank. J vfloatin in. aliquid l2having a variable level, The tanlgl l contains an l t my on L3 hich are.uspended three. m l s ati nary, le tro es 4; Hi l5;-

The "electrodes depend "irom ijhied xsppp ft m an mowing: gzfi e ime b rw may be a or n t a an a nin th i Portion; l 'l ;maybe providedwitnanopening I 8 above; ithe' liquide rheostat to provide easy aceess to ptheeostat. Depending from portion flare a plural ty of; fixedi vertieal--rod members l 9 whioh;a1 te;threaded -on their lower; ends. Each rod l9is p rovided-on the threaded portion with a nut ZU' and a lock nut 21for adjustably-support ing", the remainder; of thefixed portion of thel-iquidrheostat. Each-rod I9 is also provided with a -'horizontallyprojecting support member 22 whichrests on nut 20',- and a tubular guidemember 23 -positioned; around the rod; and attached to; memberiz' in asuitable manner. The function-'of guides Z a-is explainedindetailhereinafter p The fixedportion of the liquidrheostatill includesa metal bellmember 24; to which a pluah-W Q r mot ns are at a d in asuitable manner;such asbywelding. The members 255 rest on theprojections; 22 and are-secured thereto in a; suitable 'rnanner,suchas-by nuts and boltsZfi; thus supporting bell member 24.

' he pp r ho i onta urfa l. m m e 24, is. provided, with an opening 38which is closed y. means am -m mber 21 insulating material. Insulating,member. 21 n rn i videdwith three apertures through which extend threeIQQSTZS, "The three electrodes L4, 15 and Ifi .,are, suspended=respectively'from these three rods being attached to themin a suitablemanneltsuch as .by welding. Above. insulating member-[21, each rod j 28is provided with a terminal portion 2B which serves the dual purpose ofsupporting the rod andel'ectrodeattajched thereto and ofproviding meansfor electrical connections to the electrode. If desired, a protectivecover 3!! may be provided over the terminals 29 On opposite sides ofithebell member 24 there are. r vi ed o guide o s 3. W i Secured to thebellmember 24in a suitablemanner, such ashY-Wdd e h an H s ro i e h a pairoi bosses '3? which are seeuredto the outside of the ta nlgin operativerelation with guiderods' 31 Each of; the bosses 32"has a slot throughwhich the-guide rod passes and,'as the tank ll moves up and downresponsively to changes in the level ofyliquid l2, the guide rods 3|maintain tank I l in alignment with bell member 24. At their lowerextremities, guide rods 3| are provided with threaded portionsand aplurality of nuts 33 -and Washers 34' on these threaded portions whichsecure across member 35; Mommy-:35 provides a lowers-stop for tank II sothat tank II cannot be lowered to such an extent that electrolyte I3 isentirely out of contact with electrodes I4, I5 and It. This is a safetyfeature to provide protection in the event that the level of liquid I2should become low enough otherwise to cause the electrodes completely tolose contact with the electrolyte.

In addition to the functions already described for bell member 24, italso provides means for preventing contamination of electrolyte I 3 byliquid I2 in the event that the level of liquid I2 should riseabnormally high, and above the upper margin 33 of tank I I. Bell member24, which is otherwise completely sealed above its lower margin 39, isprovided with a vent 31 to permit the escape of air from the cavityformed by member 24, tank II and liquid I2 as the tank rises in responseto an increase in the level of liquid I2. When the level of liquid I2rises high enough to cover vent 37, this cavity, formed by the bellmember, the electrolyte tank and liquid I 2, is sealed and liquid I2 isprevented from entering the tank and contaminating electrolyte I3.

If the level of liquid I2 rises sufiiciently, the upper margin 36 oftank II comes in contact with the under surface of the upper horizontalportion of bell 24. Then, if the level of liquid I2 rises still more,the buoyancy of tank II causes the entire bell and electrode assembly torise along with the tank. In such a case, members 22' leave theirsupporting nuts 26, and the bell and electrode assembly and the tank areguided upward by guide members 23. If the level of liquid I2 continuesto rise, this upward motion continues until members 23 contact theenlarged portions 40 on rods I9. If the level of liquid I2 then risesstill further, the effect described in the preceding paragraph comesinto play, and the air trapped in the cavity formed by bell 24 and tankI I and sealed by liquid I 2 still prevents contamination of theelectrolyte I3.

If desired, the bell and electrolyte assembly may be supported at anintermediat position between the lower and upper extreme positions justdescribed, in which case guide members 23 are at an intermediateposition between nuts 20 and projections 40. The bell and electrodeassembly may be so supported by means of a supporting cable (not shown)through opening I8, or in any other suitable manner, and such supportingmeans may be made remotely adjustable, if desired. By arranging theapparatus in this manner, the limits of operation of tank II may bechanged accordingly, and this, in turn, may

be used to maintain liquid i2 at various selected levels. The manner inwhich the present apparatu may be used as a liquid level regulator isdescribed hereinafter.

It will be understood that the liquid rheostat illustrated in Figs. 1and 2 is a three-phase rheostat, with the resistance for one phase beingprovided between electrodes I4 and I5, for another phase betweenelectrodes I5 and I6, and for the third phase between electrodes I6 andIt, each of the electrodes being equidistant from the other twoelectrodes. The amount of resistance in each phase depends upon theextent to which the electrodes are submerged in the electrolyte, thegreater the extent of submersion the smaller he resistance, and viceversa.

A preferred use for our invention isin a slip regulator for a woundrotor induction motor, and a liquid rheostat suitable for thi purpose isillustrated in the drawing. The three electrodes M, 15 and I 6 may. forexample, be connected 4 through terminals 29 to the three phases of thesecondary winding of a three-phase wound rotor motor. This motor may, ifdesired, drive a pump which controls the level of liquid I2.

In such a case, if the level of liquid I2 starts to rise, tank II rises,thus causing increased portions of electrodes I 4, I5 and It to beimmersed in electrolyte I3. This decreases the resistance between eachpair of electrodes, thus decreasing the secondary resistance of thewound rotor induction motor and causing the motor to increase in speed.This increases the output of the pump controlling the level of liquid I2and thus tends to decrease the level of liquid I2 until equilibrium isestablished. Thus, it will be readily understood that an automaticregulator is provided for the level of liquid I 2.

Such liquid level regulators are widely used in many types ofinstallations, such a sewage and water supply tanks, for example, inwhich it is necessary to maintain a substantially constant liquid level,and it is of great advantage to have a simple and reliable regulatingsystem suitable for thi purpose, such as our invention makes possible.

It can be seen that our invention provides a liquid rheostat having nowearing parts and re quiring no heat exchangers, motors for raising andlowering electrodes, and other things which are necessary inconventional types of liquid rheostatss In addition, the presence or" aliquid around the tank of electrolyte conduct heat away from theelectrolyte rapidly and thus minimizes boiling, fuming, and the like, ofthe electrolyte.

While we have illustrated and described a preferred embodiment of ourinvention, many modifications thereof may be made by those skilled inthe art. Therefore, it should be understood that We intend to cover bythe appended claims any such modifications which fall within the truespirit and scope of our invention.

What we claim as new and desire to secure by Letters Patent of theUnited States is:

l. A liquid rheostat comprising a tank floatable in a liquid andarranged to rise and fall with the level of said liquid, an electricallyconductive liquid in said tank forming an electrolyte and a plurality ofelectrodes fixed with respect to said liquid and suspended in saidelectrolyte.

2. A liquid rheostat comprising a tank floatable in a'liquid andarranged to rise and fall with the level of said liquid, an electricallyconductive liquid in said tank, a support above said liquid and fixedwith respect thereto, a plurality of electrodes, and means suspendingsaid electrodes from said support in said electrically conductive liquidin variable partially immersed relation therewith.

3. A three phase liquid rheostat comprising a tank floatable in a liquidand arranged to rise and fall with the level of said liquid, an.electrically conductive liquid in said tank forming an electrolyte, andthree fixed electrodes suspended in said electrolyte, each electrodebeing substantially equidistant from the other two, the resistancebetween each pair of electrodes through said electrolyte decreasing asthe level of said liquid rises and increasing as said level falls.

4. A liquid rheostat comprising a tank floatable in a liquid andarranged to rise and fall with the level of said liquid, an electricallyconductive liquid in said tank forming an electrolyte, fixed supportmeans above said liquid, a plurality of vertically disposed electrodessuspended from said plurality of bosses support mean and partiallyimmersed in said electrolyte, and a bell member depending from saidsupport means and arranged to receive the upper portion of said tank,said upper portion rising up within said bell member when said liquidexceeds a predetermined level and forming a cavity sealed by saidliquid, the air trapped in said cavity preventing said liquid fromentering said tank and contaminating said electrolyte.

5. A liquid rheostat comprising a tank floatable in a liquid andarranged to rise and fall with the level of said liquid, an electricallyconductive liquid in said tank forming an electrolyte, fixed supportmeans above said tank, a bell member depending from said support meansand arranged to receive the upper portion of said tank when the level ofsaid liquid rises above a predetermined level, said bell member havingan opening in the upper portion thereof, an insulating member closingsaid opening, said insulating member having a plurality of apertures,and a plurality of electrodes suspended in said electrolyte through saidapertures.

6. A liquid rheostat comprising an open tank floatable in a liquid andarranged to rise and fall with the level of said liquid, said tankhaving a on the side surfaces thereof, an electrically conductive liquidin said tank forming an electrolyte, support means above said tank fixedwith respect to said liquid, a bell member depending from said supportmeans and arranged to receive the upper portion of said tank, said upperportion rising up within said bell member as said liquid rises above apredetermined level, said bell member having an opening in the upperportion thereof, an insulating member closing said opening, saidinsulating member having a plurality of apertures, a plurality ofelectrically conductive rod members extending through said apertures, aplurality of vertically disposed electrodes suspended from the lowerportions of said rods in spaced-apart relation in said electrolyte, aplurality of terminals on the upper portions of said rods above saidinsulating member for electrical connections to said electrodes, and aplurality of guide rods secured to the side surfaces of saidbell member,said guide rods cooperating with the bosses on said tank to maintainsaid tank in alignment as it rises and falls with the level of saidliquid.

7. A liquid rheostat comprising an open tank floatable in a liquid andarranged to rise and fall with the level of said liquid, an electricallyconductive liquid in said tank forming an electrolyte, a fixed supportabove said liquid, yieldable height adjusting means connected to saidfixed support, a bell member depending from said yieldable means andarranged to receive the upper portion of said tank, said bell member andsaidtank forming an air-tight cavity sealed by said liquid when theliquid rises to a predetermined level, and a plurality of electrodesinsulated from said bell member and suspended therefrom in spaced-apartrelation in said electrolyte, the upper portion of said tank rising upwithin said bell member as the level of said liquid rises until theupper margin of the tank contacts the inside upper surface of said bellmember, said bell member being carried upward by said tank when saidliquid level continues to rise and reaches a selected point above thepoint at which the upper margin of the tank contacts the bell member,the air trapped in said cavity preventing said liquid from entering thetank and contaminating the electrolyte if the level of the liquidexceeds the height of the upper margin of said tank.

8. A liquid rheostat comprising an open tank floatable in a liquid andarranged to rise and fall with the level of said liquid, said tankhaving a plurality of bosses on the side surfaces thereof, anelectrically conductive liquid in said tank forming an electrolyte, afixed support above said liquid, yieldable height adjusting meansconnected to said fixed support, a bell member depending from saidyieldable means and arranged to receive the upper portion of said tank,said bell member and said tank forming an air-tight cavity sealed bysaid liquid when the liquid rises to a predetermined level, the upperportion of said tank rising up within said bell member as the level ofsaid liquid rises until the upper margin of the tank contacts said bellmember, said bell member being carried upward by said tank when saidliquid level continues to rise and reaches a selected point above thepoint at which the tank contacts the bell member, the air trapped insaid cavity preventing said liquid from entering the tank andcontaminating the electrolyte if the level of the liquid exceeds theheight of the upper margin of said tank, a plurality of electrodesinsulated from said bell member and suspended therefrom in spaced-apartrelation in said electrolyte, a plurality of guide rods secured to theside surfaces of said bell member, said guide rods cooperating with thebosses on said tank to maintain said tank in alignment as it rises andfalls with the level of said liquid, and stop means connected to thelower extremities of said guide rods for preventing the tank fromdropping sufdciently low in response to the lowering of said liquidlevel that the electrolyte loses contact with said electrodes.

9. A rheostat comprising a tank floatable in a liquid and arranged torise and fall with the level of said liquid, said tank being adapted tocontain an electrolyte solution, and at least one electrode normallystationary with respect to said liquid and suspended in said tank.

HENRY V. CRAWFORD. LELAND J PARKINSON.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 437,412 Deprez Sept, 30, 18901,157,134 Welge Oct. 19, 1915 FOREIGN PATENTS Number Country Date186,243 France Oct. 5, 1887 526,238 Great Britain Sept. 13, 1940

